TWI635061B - Strengthened glass and methods for making the same by using heat treatment - Google Patents

Abstract

The invention provides a method for strengthening a substrate by using an exchange medium, the substrate having a width of about 25.0 mm, comprising a bulk alkali ion having an average ionic radius, and having a dimension region including a rich processing region and a lean processing region; the method comprising: heating the substrate to About 250 ° C and The heat treatment temperature after the heat treatment temperature of the highest heat treatment temperature is about 0.001-50 hours, wherein the heat treatment temperature About 325 ° C, the heat treatment time About 2 hours to produce a heat treated substrate; and exposing the heat treated substrate to the exchange medium; wherein the exchange medium comprises an invading alkali ion having an average ionic radius greater than an average ionic radius of the host alkali ion And the reinforcing substrate comprises a compressive stress layer having a depth of about 1 to 500 μm.

Description

Strengthened glass and method of manufacturing the same using heat treatment

The present invention relates to tempered glass and a method of making tempered glass.

Chemical strengthening of glass (also known as ion exchange strengthening or chemical tempering) is a technique for strengthening the prepared glass article by increasing the compression within the glass itself. It typically involves introducing larger alkali ions into the glass chemical structure to displace the smaller alkali ions already present in the structure. A common practice for chemical strengthening in glass is carried out by immersing a glass substrate containing sodium ions in a bath containing a molten potassium salt by exchanging sodium ions having a relatively small ionic radius with potassium ions having a relatively large ionic radius.

Chemical strengthening is often used to increase the compression in the glass. The increased compression in the glass portion of the glass portion is associated with increased strength in the glass, increased wear resistance, and/or increased thermal shock resistance. The increased compression can be introduced into various depths in the glass and often performed within the glass surface layer. Chemical strengthening is commonly used to treat flat glass. But it can also be used to process non-flat glass items such as cylinders and other shapes with greater geometric complexity.

Flat glass is typically manufactured using a number of known techniques. Such techniques include floating glass processes and draw processes such as melt down draw and slot draw. However, the prepared flat glass articles may vary in their chemical composition and/or structure at different locations in the glass. For example, flat glass made using floating glass technology is often prepared by spreading a softened glass material onto a molten metal surface, such as tin. Then cool the glass to shape Solid glass plate. Therefore, the prepared flat glass often contains a relatively large amount of tin on the side closer to the molten tin, and the concentration of tin is usually large near the side surface.

Chemical strengthening is often used to treat glass that has a change in chemical composition and/or structure at different locations in the glass. These changes result in locations where ion exchange and/or compression development in chemical strengthening is rich or lean relative to each other. When chemical strengthening is used to treat the glass, the introduced compressive stress is often unevenly distributed.

When the compressive stress is unevenly distributed in the chemically strengthened glass, this can introduce a bending moment in the glass by chemical strengthening treatment and then introduce an induced curvature. The effect of introducing induced curvature by chemical strengthening is especially pronounced for glass articles of smaller width. This situation is often problematic in flat glass with a small width, such as less than 25 mm, because the bending moment in thinner glass introduces greater curvature by chemical strengthening. A floating glass substrate having a width of 2.0 mm or less, and particularly a floating glass substrate having a width of 1.0 mm or less, often has a problem of having a highly significant curvature introduced by chemical strengthening.

Induced curvature is often undesirable and is particularly problematic in thin flat glass articles that require enhanced physical properties associated with chemical strengthening (but without significant induced curvature) in accordance with the manufacturing instructions. For example, the glass used in many manufactured electronic articles, such as displays for "smart" mobile phones, often requires a display glass that is substantially flat and has high strength and wear resistance.

Chemical strengthening of thin flat glass substrates, such as articles having two major surfaces and variations in chemical structure or composition within the glass, is often associated with non-equivalent intrusive alkali ion interdiffusion and/or compression generation properties between the major surfaces of the substrate. . The effect is that the local forces in the glass in relation to the distance from the median plane to the median plane of the glass article are not equal when compared, since such forces are present from the lean processing surface to the intermediate plane and from the rich processing surface to the intermediate plane. Thus, the net bending moment in the glass at about the median plane is non-zero (i.e., there is a non-zero net bending moment of stress in the midplane). Therefore, bending stress is generated.

For glass articles with thin cross sections, the bending stress from chemical strengthening is often Self-flattening deflection occurs in glass articles. This situation is especially common in glass made by the floating glass process. However, deflection is also produced in glass made by other methods which have variations in the chemical structure or composition within the glass. Thin glass made using a floating glass process often exhibits a measurable curvature after chemical strengthening. The direction of curvature is often concave on the surface that is "poor" in allowing diffusion of alkali ions to interdiffuse and is convex on the surface that is "rich" in allowing interdiffusion of alkali ions.

In recent years, various attempts have been made to overcome the problem of induced curvature associated with chemical strengthening of glass. One method involves grinding and polishing a glass substrate prior to chemical strengthening. Grinding and polishing to remove portions of the glass that differ in chemical composition and/or structure. An example of such a method is the grinding and polishing of flat glass made by a float process to remove a surface layer containing a large amount of tin. However, grinding and polishing of floating glass often introduces wear and can introduce other physical defects. These defects are severely affected by the increased time and expense associated with performing grinding and polishing.

Other methods have involved secondary chemical treatment of the prepared glass prior to chemical strengthening. Secondary chemical treatment is utilized to address chemical composition and/or structural differences at different locations in the glass. However, secondary chemical treatment can alter the physical properties of the glass and otherwise degrade the glass produced by subsequent chemical strengthening. In addition, like grinding and polishing, the secondary chemical treatment involves the time and expense of additional processing prior to chemical strengthening.

In view of the foregoing, there is a need for a method of chemically strengthening glass and making a chemically strengthened glass wherein the strengthened glass has a reduced induced curvature. There is also a need for tempered glass that does not have the drawbacks associated with grinding and polishing or secondary chemical processing applied in prior methods associated with chemical strengthening of glass. It is also desirable that the tempered glass having a reduced induced curvature also has improved physical properties of the chemically strengthened glass, such as higher strength, higher wear resistance, and/or higher thermal shock resistance.

This summary is provided to introduce a selection of concepts. Combined with the following in the embodiment The drawings further describe such concepts. This Summary is not intended to identify key features or essential features of the claimed subject matter, and is not intended to assist in determining the scope of the claimed subject matter.

According to one implementation, there is a method of manufacturing a reinforced substrate. The method includes providing a substrate. The substrate provided may have A width of about 25.0 mm. The substrate provided may be characterized by having a glass chemical structure comprising a bulk alkali ion having an average ionic radius in the glass chemical structure. The substrate provided may be characterized by having a dimensional region comprising a treatment-rich volume and a treatment-poor volume disposed opposite each other in the provided substrate. The method includes heating the provided substrate to a heat treatment temperature for a heat treatment time to produce a heat treated substrate. Heat treatment temperature About 250 ° C and The highest heat treatment temperature. The heat treatment time may be about 0.001-50 hours to produce a heat treated substrate, and if the heat treatment temperature is For one of about 325, 350 or 400 ° C, the heat treatment time can be About 2 hours. The method can include providing an exchange medium. The exchange medium can include invading alkali ions having an average ionic radius greater than the average ionic radius of the bulk alkali ions. The method can include exposing the heat treated substrate to an exchange medium. The method can include ion exchange to produce a strengthened substrate while exposing the heat treated substrate to an exchange medium. The reinforced substrate may include a compressive stress layer having a depth of about 1-500 μm.

The substrate provided preferably has Width of about 2.0 mm. The heat treatment temperature is preferably about 450 to 650 °C. The heat treatment temperature is preferably about 400 to 750 °C. Preferred if the heat treatment temperature Heat treatment time at about 400 ° C About 2 hours. The reinforced substrate preferably has a compressive stress layer having a depth of about 5 to 200 μm. The ion exchange is preferably carried out during an ion exchange time of from about 0.1 to 50 hours. The ion exchange is preferably carried out at an ion exchange temperature of from about 200 ° C to 1,400 ° C. The substrate provided is preferably flat. Preferably, the heat treatment time 0.5 hour, and if the heat treatment time is about 0.5-1 hour, the heat treatment temperature About 500 ° C; if heat treatment time Heat treatment temperature for about 1-3 hours About 475 ° C; if heat treatment time Heat treatment temperature for about 3-6 hours About 450 ° C; if heat treatment time Heat treatment temperature for about 6-12 hours About 425 ° C; if heat treatment time Heat treatment temperature for about 12-18 hours About 400 ° C; and if heat treatment time Heat treatment temperature for about 18-25 hours About 375 ° C. Preferably, the heat treatment time 0.5 hour, and if the heat treatment time is about 0.5-1 hour, the heat treatment temperature About 575 ° C; if heat treatment time Heat treatment temperature for about 1-3 hours About 550 ° C; if heat treatment time Heat treatment temperature for about 3-6 hours About 525 ° C; if heat treatment time Heat treatment temperature for about 6-12 hours About 500 ° C; if heat treatment time Heat treatment temperature for about 12-18 hours About 475 ° C; and if heat treatment time Heat treatment temperature for about 18-25 hours About 450 ° C. Preferably, the heat treatment time 0.5 hour, and if the heat treatment time is about 0.5-1 hour, the heat treatment temperature About 650 ° C; if heat treatment time Heat treatment temperature for about 1-3 hours About 625 ° C; if heat treatment time Heat treatment temperature for about 3-6 hours About 600 ° C; if heat treatment time Heat treatment temperature for about 6-12 hours About 575 ° C; if heat treatment time Heat treatment temperature for about 12-18 hours About 550 ° C; and if heat treatment time Heat treatment temperature for about 18-25 hours About 525 ° C. The method preferably further comprises cooling the heat treated substrate to a cooling temperature of about 150 ° C to produce a cooled heat treated substrate; and heating the cooled heat treated substrate to About 250 ° C and The heat treatment temperature of the highest heat treatment temperature is followed by a heat treatment time of about 0.01 to 50 hours to produce a heat-treated substrate. Preferably, the substrate provided comprises at least one of a chemical composition and a chemical structure in the substrate, and at least one of a chemical composition and a chemical structure in the lean region is different from that in the rich treatment region. The exchange medium is preferably one of a liquid, a solid, a gas, and a mixture thereof. The rich treatment zone and the lean treatment zone are preferably disposed diametrically opposite each other in the substrate. The method is preferably one of a continuous process and a batch process. The substrate provided preferably comprises one of an alkali aluminosilicate glass and a soda lime silicate glass.

According to another implementation, there is an article of manufacture. The article includes a reinforced substrate. The reinforcing substrate may have A width of about 25.0 mm. The reinforcing substrate may have a compressive stress layer having a depth of about 1-500 μm. The strengthened substrate may be characterized by having a glass chemical structure comprising alkali ions in a glass chemical structure. The reinforced substrate can have dimensional regions including a rich processing region including a rich surface of the substrate and a lean processing region including a poor surface of the substrate. The lean treatment zone may be characterized by at least one of a chemical composition and a chemical structure being different from the rich treatment zone. The reinforced substrate can also include a body region within the substrate adjacent at least one of the rich processing region and the lean processing region. The strengthened substrate can include a metal concentration in at least one of the lean processing region and the rich processing region. The concentration of metal in at least one of the lean region and the rich region may be higher than the concentration of metal in the body region About 0.4% by mole. The metal concentration in the lean treatment zone can be higher than the metal concentration in the rich treatment zone. The strengthened substrate may include an alkali ion concentration in a diffusion depth of at least one of the rich processing region and the lean processing region. The alkali ion concentration in the diffusion depth of at least one of the rich treatment zone and the lean treatment zone may be higher than the alkali ion concentration in the bulk region About 0.5% by mole.

At least one of the rich treatment zone and the lean treatment zone preferably has a diffusion depth of about 5 to 150 μm. The tempered glass substrate preferably comprises greater than 50 mole% SiO _2. The chemically strengthened glass substrate preferably contains a total of about 1 to 25 mol% of Li ₂ O+Na ₂ O+K ₂ O in the diffusion depth, wherein the diffusion depth is about 5 to 150 μm. The net bending moment at about the median plane in the reinforced substrate is preferably about zero.

According to another implementation, there is an article of manufacture. The article includes a reinforced substrate. The reinforcing substrate may have a compressive stress layer having a depth of about 1-500 μm. The reinforced substrate can be fabricated by a process. The process includes providing a substrate. The substrate provided may have A width of about 25.0 mm. The substrate provided may be characterized by having a glass chemical structure comprising a bulk alkali ion having an average ionic radius in the glass chemical structure. The substrate provided may be characterized by having a dimensional region comprising a rich processing region and a lean processing region disposed opposite each other in the provided substrate. The method includes heating the provided substrate to a heat treatment temperature for a heat treatment time to produce a heat treated substrate. Heat treatment temperature About 250 ° C and The highest heat treatment temperature. The heat treatment time may be about 0.001-50 hours or about 0.01-20 hours to produce a heat treated substrate, and if the heat treatment temperature is For one of about 325, 350 or 400 ° C, the heat treatment time can be About 2 hours. The method can include providing an exchange medium. The exchange medium can include invading alkali ions having an average ionic radius greater than the average ionic radius of the bulk alkali ions. The method can include exposing the heat treated substrate to an exchange medium. The method can include ion exchange to produce a strengthened substrate while exposing the heat treated substrate to an exchange medium.

The above summary is not intended to describe each embodiment or every implementation. Other features, their nature and various advantages are described in the following figures, as well as the examples and embodiments below.

100‧‧‧Chemical strengthening process including heat treatment

200‧‧‧ schema

300‧‧‧An exemplary process for producing a reinforced substrate with reduced induced curvature by heat treatment

One or more of the embodiments described herein are described in conjunction with the specification and are described in conjunction with the specification. In addition, it should be understood that the drawings are presented for purposes of example only. In the drawings: FIG. 1 is a flow chart illustrating an exemplary overview of the implementations described herein; FIG. 2 is a diagram showing the properties of an exemplary reinforced substrate fabricated by heat treatment prior to chemical strengthening; and FIG. A flow chart for illustrating an exemplary process for fabricating a reinforced substrate using heat treatment.

The following embodiments are referred to with the accompanying drawings. The same reference numbers in different figures may identify the same or similar elements.

Overview

The present invention is applicable to the manufacture of chemically strengthened glass and has been found to be particularly advantageous for the manufacture of chemically strengthened glass having a reduced induced curvature. In accordance with the principles of the present invention, chemically strengthened glass does not have the drawbacks associated with chemically strengthened glass produced by grinding and polishing or secondary chemical treatment prior to chemical strengthening. Although the present invention is not necessarily limited to such applications, various aspects of the invention are apparent from the discussion of various examples.

1 is a flow chart illustrating an illustrative overview of the implementations described herein. Assumed glass base The plates vary in their chemical composition and/or chemical structure at different locations or "zones" in the glass. One type of change exists in areas that have chemical compositions and/or chemical structures that are more susceptible to chemical strengthening treatment. This area is the "rich processing" area. Another type of variation exists in areas having chemical compositions and/or chemical structures that are less susceptible to chemical strengthening treatment. This is the "poor treatment" area.

The term "rich treatment zone" refers to the region of the glass substrate that exhibits faster inter-alkali ion interdiffusion and/or greater compression development during chemical strengthening relative to the "lean treatment zone" under equivalent chemical strengthening conditions applied to the glass substrate. The regions may appear in spaces or layers below or below the surface of the substrate. The rich treatment zone or the lean treatment zone may be a surface layer of a glass substrate in which diffusion of invading alkali ions extends to a given "diffusion depth" from the surface, also referred to as penetration depth or diffusion layer. In chemical strengthening, one part of the diffusion depth is in the compressive stress, which is called "compressive stress layer" or "hardening depth". The depth of hardening is the width of the diffusion layer in the compressive stress in the specimen. The "body region" in the glass is an area that is not affected by the diffusion of invading alkali ions. The body region may be present in the glass region below or adjacent to the diffusion depth of the invading alkali ions or other types of ions in the glass.

In accordance with the principles of the present invention, the substrate provided is treated under heat in a "heat treatment" prior to chemical strengthening to form a "heat treated substrate." The heat treatment can be performed by exposing the supplied substrate to "heat treatment temperature" for "heat treatment time". The amount of time and temperature used for heat treatment prior to chemical strengthening is significantly different in the case of various types of glass.

Applicants have discovered that by using a heat treatment process prior to chemical strengthening to create a heat treated substrate, the induced curvature is reduced in the chemically strengthened substrate. The induced curvature reduction associated with heat treatment is particularly pronounced in thinner glass substrates such as glass substrates having a width of about 25.0 mm or less. A significant reduction in induced curvature has also been demonstrated in glass substrates having a deeper depth of hardening that occurs during chemical strengthening. Deeper hardening depths can be produced in different ways, such as by utilizing extended ion exchange in ion exchange for chemical strengthening Time and / or higher ion exchange temperature to carry out.

As shown in FIG. 1, an exemplary implementation of a chemical strengthening process 100 including heat treatment is demonstrated.

At step 102, a "thin" glass substrate is provided having at least two distinct regions, namely a rich processing region and a lean processing region as described above.

At step 104, a heat treatment is applied to the provided substrate by exposing the glass to a temperature T for a period of time P. The time P can be different and can be affected by the temperature of T in the heat treatment. A lower T temperature may take a longer time P to achieve a significant reduction in induced curvature. In general, the shortest period of time for P is at least about 0.001 hours and the longest period of time for P can be as high as 50 hours or longer. In general, the minimum temperature of T is at least about 250 ° C, and the maximum temperature of T can reach the highest heat treatment temperature. If heat treatment temperature About 325 ° C or About 400 ° C, the heat treatment time can be About 2 hours. The heat treatment temperature may be about 400-750 ° C or about 450-650 ° C.

The highest heat treatment temperature is the temperature at which the glass can be deformed or liquefied and can vary depending on the type and nature of the glass and glass substrate. Those skilled in the art understand that deformation is caused by the viscosity of the glass that decreases rapidly with increasing temperature. Thus, shorter heat treatment times and/or lower heat treatment temperatures can be used in order to avoid measurable deformation in the glass substrate undergoing heat treatment in accordance with the principles of the present invention. If measures are taken to prevent deformation of the substrate to be subjected to heat treatment, such as by adding a support around the substrate subjected to heat treatment, the presence of the support helps to prevent deformation of the substrate and increase the maximum heat treatment temperature of the substrate. For example, some soda-calcium silicate glass substrates have a maximum heat treatment temperature of about 500 ° C to 800 ° C. In another example, some of the sodium aluminosilicate glass substrates have a maximum heat treatment temperature of from about 600 °C to 900 °C. The deformation temperatures of most types of glass compositions and glass substrates known for use in chemical strengthening applications are well known to those skilled in the art.

At step 106, the heat treated substrate is exposed to an exchange medium for ion exchange to produce a strengthened glass substrate. Compressive stress layer or hardened depth during ion exchange The degree is developed in the heat-treated substrate to form a strengthened glass substrate. When the exchange medium is applied in step 106, chemical strengthening is performed to produce a strengthened substrate having an induced curvature that has been reduced because a smaller measurement of the induced curvature is produced by the heat treatment. Without wishing to be bound by any particular theory, the heat treatment prior to ion exchange appears to reduce the induced curvature that would otherwise be produced by chemical strengthening of the glass substrate.

The present invention has been described with reference to the embodiments, principles, and examples thereof for the purpose of illustration and description. In the following description, numerous specific details are set forth in order to provide a However, it will be readily apparent that the embodiments may be practiced without limitation to the specific details. In other instances, some embodiments have not been described in detail so as not to unnecessarily obscure the description. Further, various embodiments are described below. Embodiments may be used or executed in different combinations.

The operation and function of certain embodiments can be more fully understood from the examples described below. The examples on which these examples are based are merely representative. The choice of such embodiments for illustrating the principles of the present invention does not indicate that the materials, components, reagents, conditions, techniques, configurations, designs, etc., which are not described in the examples, are not suitable for use, or are not described in the examples. Excluded from the scope of the accompanying patent application or its equivalent. The meaning of the examples can be better understood by comparing the results obtained therefrom with comparable results that can be obtained from testing or testing, which may or may have been designed to serve as a control experiment and provide a basis for comparison.

As used herein, the terms "based on", "comprises", "comprising", "includes", "including", "has", "having" Or any other variation thereof is intended to cover non-exclusive inclusions. For example, a process, method, article, or device that comprises a list of elements is not necessarily limited to those elements, but may include other elements not specifically listed or inherent to the process, method, article, or device. In addition, unless expressly stated to the contrary, "or" is meant to be inclusive or non-exclusive. For example, condition A or B is full by any of the following Foot: A is true (or exists) and B is false (or non-existent), A is false (or non-existent) and B is true (or exists), and both A and B are true (or present). In addition, "a" or "an" is used to describe elements and components. This is done for convenience only and gives the general meaning of the description. This description should be read to include one or a singular, and the singular includes the plural unless the meaning is otherwise.

The meanings of abbreviations and some terms used herein are as follows: "mm" means millimeter, "μm" means micrometer or micron, "g" means gram, "mg" means milligram, "μg "M" means liters, "L" means liters, "mL" means milliliters, "cc" means cubic centimeters, "cc/g" means cubic centimeters / gram, "mol" means mur, "mmol" It means nothing, "wt%" means weight% and "mol%" means mol%.

Exemplary substrate glass

As used herein, a "glass substrate" can comprise any type of ion exchangeable glass or a glass-ceramic in which the ion exchangeable phase is glass. Examples of glass include soda lime silicate glass, alkali aluminosilicate glass or alkali aluminoborosilicate glass, but encompass other glass compositions, including wherein the glass forming component does not contain cerium oxide, such as boron trioxide. Glass such as (borate), phosphorus oxide (phosphate), or alumina (aluminate). As used herein, "ion exchangeable" means that the glass is capable of exchanging glass located in the glass with a larger alkali ion (ie, "invasive alkali ion") from an exchange medium (which may be a liquid, a solid, a gas, or a mixture thereof). Alkali ions (ie, "host alkali ions") in the structure (such as at or near the surface of the substrate). "Ion exchange rate" refers to the amount of invading ions entering the substrate over a period of time. The glass may have chemical composition and/or chemical structural changes at various locations or "zones" in the glass. An example of a change in chemical composition is an excess of a metal, such as a metal ion or other form of metal, and may include a metallic species such as tin or lead. An example is a metal such as tin remaining in a flat glass made by a floating glass process. An example of a chemical structural change is the presence of an element in the glass, wherein the element may have different valences throughout the different regions, such as tin being present in different regions as Sn ²⁺ and Sn ⁴⁺ valences. In this example, different forms of tin form different chemical structures in different regions.

Illustrative embodiments of substrate glass include silicate glass, such as soda-calcium silicate glass or sodium aluminosilicate glass, which includes aluminum oxide, at least one alkali metal, and in some embodiments, greater than 50 mole % SiO ₂ , In other embodiments at least 58 mole % SiO ₂ and in other embodiments at least 60 mole % SiO ₂ . An exemplary embodiment of a glass substrate includes a substrate having one or more widths of, for example, about 25, 20, 15, 10, 8, 6, 5, 4, 3, 2, 1, 0.7, 0.5, 0.25, and 0.1 mm. The common width and type of substrate glass is a test piece cut from a mother sheet of floating glass having a width of 0.7 mm. The length and cross-sectional area of an exemplary test piece can vary and can be flat or curved in one portion of the substrate prior to chemical strengthening.

Exemplary heat treatment parameters

Without wishing to be bound by any particular theory, the heat treatment appears to cause some chemical change or reaction in at least the lean region of the glass substrate in accordance with the principles of the present invention. This change can occur via diffusion of chemicals from the atmosphere surrounding the substrate or other external media. Or the chemical change or reaction can occur from within the lean treatment zone itself.

Applicants have discovered that the heat treatment process can be applied to achieve a desired reduction in induced curvature when applied to a glass substrate prior to chemical strengthening prior to the principles of the present invention. The heat treatment temperature and heat treatment time can be roughly estimated using an empirical relationship relating to the maximum heat treatment temperature of the glass substrate and the reduced induced curvature of the desired amount. The empirical relationship is:

Wherein "t" is the heat treatment time (hours), "n" is the empirical constant, "m" is the highest heat treatment temperature (°C), and "T" is the heat treatment temperature (°C).

Therefore, the heat treatment time "t" can be determined for the glass substrate having the highest heat treatment temperature "m" for a given heat treatment temperature "T". Those who are familiar with the proliferation science can also understand The width of the reaction layer affected by diffusion will increase with the square root of time. Therefore, a higher temperature or a longer period of time facilitates a higher reduction in induced curvature. At higher temperatures, shorter heat treatment times may be sufficient, while at lower temperatures, longer heat treatment times may be used.

For example, for a soda lime silicate glass substrate having a width of less than about 2 mm but more than about 0.25 mm, suitable values for "n" and "m" may be 0.00111 hours/(°C) ² and 600 ° C, respectively. Therefore, for these soda-calcium silicate glass substrates, if heat treatment time Heat treatment temperature for about 1 hour About 575 ° C. If heat treatment time Heat treatment temperature for about 3 hours About 550 ° C. If heat treatment time Heat treatment temperature for about 6 hours About 525 ° C. If heat treatment time Heat treatment temperature for about 12 hours About 500 ° C. If heat treatment time Heat treatment temperature of about 18 hours About 475 ° C. If heat treatment time Heat treatment temperature of about 25 hours About 450 ° C.

The heat treatment temperature that can be used can vary widely and can be kept constant or averaged over different temperatures. Illustrative examples of heat treatment temperatures that can be used for heat treatment include from about 250 °C to 1,500 °C. For some types of soda-calcium silicate glasses, heat treatment temperatures above about 450 ° C and preferably above about 500 ° C can be used. Other exemplary heat treatment temperatures for various types of glass include temperatures of about 250, 300, 400, 500, 600, 700, 800, 900, 1,000, 1, 100, 1, 200, 1, 300, 1, 400, and 1,500 ° C or higher.

The heat treatment time period that can be used can vary widely and can be continuous or discontinuous. Illustrative examples of heat treatment times that can be used for heat treatment include from about 0.001 to 50 hours. For some types of soda-calcium silicate glass, for example, a heat treatment time of about 1 to 6 hours can be used. Other exemplary heat treatment times for various types of glass include about 0.001, 0.01, 0.1, 0.5, 1, 2, 4, 5, 6, 8, 10, 20, 25, and 50 hours or longer (in hours). .

Heat treatment time according to an exemplary embodiment 0.5 hour and if the heat treatment time is about 0.5-1 hour, the heat treatment temperature used About 575 ° C; if heat treatment time Heat treatment temperature for about 1-3 hours About 550 ° C; if heat treatment time Heat treatment temperature for about 3-6 hours About 525 ° C; if heat treatment time Heat treatment temperature of about 6-12 hours About 500 ° C; if heat treatment time Heat treatment temperature of about 12-18 hours About 475 ° C; and if heat treatment time Heat treatment temperature of about 18-25 hours About 450 ° C.

Heat treatment time according to another exemplary embodiment 0.5 hour and if the heat treatment time is about 0.5-1 hour, the heat treatment temperature used About 500 ° C; if heat treatment time Heat treatment temperature for about 1-3 hours About 475 ° C; if heat treatment time Heat treatment temperature for about 3-6 hours About 450 ° C; if heat treatment time Heat treatment temperature of about 6-12 hours About 425 ° C; if heat treatment time Heat treatment temperature of about 12-18 hours About 400 ° C; and if heat treatment time Heat treatment temperature of about 18-25 hours About 375 ° C.

Heat treatment time according to another exemplary embodiment 0.5 hour and if the heat treatment time is about 0.5-1 hour, the heat treatment temperature used About 650 ° C; if heat treatment time Heat treatment temperature for about 1-3 hours About 625 ° C; if heat treatment time Heat treatment temperature for about 3-6 hours About 600 ° C; if heat treatment time Heat treatment temperature of about 6-12 hours About 575 ° C; if heat treatment time Heat treatment temperature of about 12-18 hours About 550 ° C; and if heat treatment time Heat treatment temperature of about 18-25 hours About 525 ° C.

Exemplary tempered glass

Illustrative examples of chemically strengthened glass include soda lime silicate glass and sodium aluminosilicate glass that are fortified in a bath such as a potassium nitrate bath. The chemical strengthening of the fabricated tempered glass can be performed over a wide range of applied ion exchange temperatures during a wide range of ion exchange time periods.

The ion exchange temperature that can be used varies widely and can be an average of constant or different temperatures. Illustrative examples of ion exchange temperatures available for ion exchange include from about 200 °C to 1,400 °C. For some types of soda-calcium silicate glasses, ion exchange temperatures above about 400 ° C and preferably above about 430 ° C can be used. Other exemplary departures of various types of glass The sub-exchange temperature includes about 200, 300, 400, 500, 600, 700, 800, 900, 1,000, 1, 100, 1, 200, 1, 300, and 1,400 ° C or higher.

The ion exchange time period that can be used can vary widely and can be continuous or discontinuous. Illustrative examples of ion exchange times that can be used to perform ion exchange include from about 0.1 to 50 hours. For some types of soda-calcium silicate glasses, for example, ion exchange times of about 1 to 5 hours can be used. Other exemplary ion exchange times for various types of glass include about 0.01, 0.1, 0.5, 1, 2, 4, 5, 6, 8, 10, 20, 25, and 50 hours or longer (in hours).

The area of compressive stress can vary and is, for example, about 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 200, 300, 400, 500, and 600 μm of the substrate glass surface. Developed within the depth of diffusion. According to an exemplary embodiment, the compressive stress in the strengthened glass substrate is greatest at the surface of the glass (ie, "surface compression"), and the degree of compressive stress may follow a gradient extending downward from the surface through the depth of hardening in the tempered glass. .

In an exemplary embodiment, the amount of surface compressive stress (i.e., surface compression) can vary from 100 to 2,000 MPa. In an exemplary embodiment, the surface compressive stress can be in the range of up to about 800 MPa or more in the reinforced soda lime silicate glass and up to about 1,200 MPa or more in the aluminosilicate glass. In certain exemplary embodiments, the surface compression is about 200-650 MPa in the reinforced soda lime silicate glass and about 300-850 MPa in the aluminosilicate glass. In other exemplary embodiments, the surface compression is about 400-600 MPa in the reinforced soda lime silicate glass and about 600-800 MPa in the aluminosilicate glass.

In certain exemplary embodiments, the fortified bismuth glass, such as soda-calcium silicate glass or sodium aluminosilicate glass, comprises alumina, at least one alkali metal, and in some embodiments, greater than 50 mole % SiO ₂ , In other embodiments at least 58 mole % SiO ₂ and in other embodiments at least 60 mole % SiO ₂ . In such embodiments, the total molar % of Li ₂ O+Na ₂ O+K ₂ O is, for example, at least about 1, 2, 5, 7, or 8-10 mol% in the region associated with the depth of diffusion and 25 mol%, preferably 20% by mole, and better About 2, 5, 7, 8, 10, 12, 15, or 16-18% of the mole.

In another exemplary embodiment, the alkali aluminosilicate glass comprises, consists essentially of, or consists of: 60-75 mole % SiO ₂ ; 5-15 mole % Al ₂ O ₃ ; 0-12 mol % B ₂ O ₃ ; 8-21 mol % Na ₂ O; 0-8 mol % K ₂ O; 0-15 mol % MgO; and 0-3 mol % CaO. In such embodiments, the total molar % of Li ₂ O+Na ₂ O+K ₂ O is, for example, at least about 1, 2, 5, 7, or 8-10 mol% in the region associated with the depth of diffusion and 25 mol%, preferably 20% by mole, and better About 2, 5, 7, 8, 10, 12, 15, or 16-18% of the mole.

In another embodiment, the alkali aluminosilicate glass substrate comprises, consists essentially of, or consists of: 60-70 mole % SiO ₂ ; 6-14 mole % Al ₂ O ₃ ; 0-15 mol % B ₂ O ₃ ; 0-15 mol % Li ₂ O; 0-20 mol % Na ₂ O; 0-10 mol % K ₂ O; 0-15 mol % MgO; 0-10 mol % CaO; 0-5 mol % ZrO ₂ ; 0-2 mol % SnO ₂ ; 0-1 mol % CeO ₂ ; of which about 1, ₂ , 5, 7, 8 or 10 -12% by mole Li ₂ O+Na ₂ O+K ₂ O About 2, 5, 7, 8, 10, 12, 15 or 16-20% of the mole, such as in the region related to the depth of diffusion, and 0% by mole MgO+CaO 15 moles %.

In an exemplary embodiment, sodium ions in the substrate glass are replaced by potassium ions from the molten bath, but other alkali metal ions (such as ruthenium or osmium) having a larger atomic radius can displace the smaller alkali metal ions in the glass. Similarly, other alkali metal salts such as, but not limited to, nitrates, sulfates, halides, and the like can be used in the ion exchange process.

An illustrative embodiment of a tempered glass substrate includes A substrate of one or more widths of about 25, 20, 15, 10, 8, 6, 5, 4, 3, 2, 1, 0.7, 0.5, 0.25, and 0.1 mm. The length and cross-sectional area of the reinforced substrate may vary. For example, tempered glass can be a sheet produced in a continuous process. In another example, the tempered glass can be a test piece produced in a batch process.

In another exemplary embodiment, the chemically strengthened glass substrate may have at least one compressive stress layer (ie, a depth of hardening) having a depth of about 1,000, 500, 250, 150, 100, 90, 80, 70, 60, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 1 μm or less.

In another exemplary embodiment, the chemically strengthened glass substrate may have a surface compression of about 100 MPa or more (eg, about 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, or 2000 MPa or more). Stress, about 1 μm or more (for example, about 5, 10, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 μm or more Hardening depth of about 1 μm or more (for example, about 5, 10, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100) The diffusion depth of 125 nm or 150 μm or more.

In another exemplary embodiment, the chemically strengthened glass substrate can have a higher amount of metal in at least one surface region or layer, such as a rich processing region or a lean processing region, than in a body region adjacent to such surface regions. The metal concentration in at least one of the lean region and the rich region may be higher than the metal concentration in the body region About 0.4, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 8.0, 10.0, 12.0, 15.0, 20 or 25 mol% (mol%). According to an embodiment, the metal concentration in the lean treatment zone is higher than the metal concentration in the rich treatment zone. An example of a tempered glass having different metal concentrations in different regions is a chemically strengthened glass made of a flat glass substrate prepared by tin using a floating glass process.

In another exemplary embodiment, the chemically strengthened glass substrate may have an average concentration of alkali ions (eg, invading alkali ions and bulk alkali ions) that is in the diffusion depth of the surface region as compared to in adjacent regions such as the body region. Same or different. The surface area can be a rich or poorly treated area in the tempered glass. The average concentration of alkali ions may be the same or different from the average concentration of alkali ions in adjacent regions such as the body region. In an exemplary embodiment, the average concentration of alkali ions in the diffusion depth of the surface region is higher than the concentration of alkali ions in the bulk region. Up to about 0.5 mol%. In other embodiments, the average concentration of alkali ions in the diffusion depth of the surface region is higher than the concentration of alkali ions in the body region adjacent to the surface region. To about 0.4, 0.3, 0.2, 0.1 or 0.05 mol%, equal to or less than this concentration.

Exemplary exchange medium

Illustrative examples of liquid exchange media that can be used for chemical strengthening include liquid molten salt baths. The melt bath includes invading alkali ions having an average ionic radius greater than the average ionic radius of the host alkali metal ions in the substrate glass in the alkali metal ions of the molten salt prior to ion exchange. Common examples of liquid molten salt baths include potassium as the invading alkali ion to replace the potassium nitrate of the sodium and/or lithium bulk ions in the substrate glass.

Mixed salt blends of invading alkali ions can also be used as liquid exchange media. Such blends may include salts of different alkali metals, preferably different alkali metal nitrates. The nitrate melt blend can include at least two different alkali ions, such as Na and K, or Na and Rb, or K and Rb, or K and Cs. However, it is also possible to include three or four different alkali metals. The method according to the embodiment provides the option of efficiently incorporating the invading alkali ions having an ionic radius substantially larger than the radius of the host alkali ion (such as lithium or sodium ions) into the treated glass article.

Illustrative embodiments of solid exchange media that can be used for chemical strengthening include semi-solid pastes that can be applied to the surface of a glass substrate. The paste includes invading alkali ions from a source such as a salt and at least one rheological agent such as clay to suspend the ions in the solid exchange medium. Kaolin is a common example of a rheological agent that can be used to make solid exchange media. The viscosity of the paste made with kaolin can be modified with water and other additives to suit the application of the paste to the glass substrate. The water content of the paste can be evaporated using elevated elevated temperatures (such as greater than 120 °C) prior to application as a solid exchange medium. Another example of a rheological agent is an aluminosilicate fiber. Other clays and rheological agents are also covered.

In addition to liquid and solid exchange media, gas exchange media and mixtures thereof are also contemplated. The exchange medium can include a composition that affects the ion exchange rate of the invading alkali ions in the exchange medium. This composition increases or decreases the ion exchange rate of the invading alkali ions into the substrate. This composition can be varied in many different ways to affect the rate of ion exchange associated with the exchange medium, such as by the addition of additives that slow the rate of ion exchange.

Instance

The following examples demonstrate the method of making chemically strengthened glass using a heat treatment process.

Example 1

Example 1 demonstrates the preparation of chemically strengthened soda lime silicate glass with reduced induced curvature.

Sample preparation: A sodium calcium silicate glass test piece (50 mm × 50 mm diameter and 0.4 mm width) was cut from a mother sheet formed by a tin floating glass process. The test piece was heat-treated in air (oxidizing atmosphere) at 550 ° C for 2.0 hours in a muffle furnace. The test piece was then chemically strengthened by immersing the test piece directly from the muffle furnace into a beaker of molten KNO ₃ controlled to a temperature of 440 ° C for 8 hours. The test piece was cooled and rinsed with water to remove the solidified salt. Check a minimum of two test strips for each parameter. The treated specimen deflection was measured from the measured surface profile using a non-contact optical plotter. Flexure is the peak-to-valley height measured along the line drawn between the midpoints of the opposite edges of the square test piece.

Results: The average deflection relative to the pretreatment parameters is given in Table 1 below, where positive deflection indicates the convex curvature of the rich surface and negative deflection indicates the concave curvature of the rich surface. For commercial purposes, such as for use in personal electronic devices and flat panel displays, acceptable deflection is currently about 0.1% linear span and 50 micron for 50 mm span.

Table 1: Heat treatment (given in temperature (degrees Celsius) and time (hours)) and average deflection (micron) after chemical strengthening.

The heat treatment in air at 550 ° C for 2.0 hours prior to chemical strengthening produces a deflection of less than 50 microns target in this case. The surface compression and hardening depth resulting from chemical strengthening is measured using an ellipsometer. For the heat-strengthened test piece after chemical strengthening, the average deflection is 42.7 μm (rich side convex surface), and the average surface compression is 705 MPa for the rich surface and for the poor surface The face was 737 MPa and the average hardening depth was 13.8 microns for the rich surface and 12.4 microns for the lean surface.

Comparative test pieces that did not undergo heat treatment but undergo equivalent chemical strengthening had an average deflection of 94.7 microns (rich side convexity).

Example 2

Example 2 demonstrates the preparation of chemically strengthened soda-calcium silicate glass for a longer period of time with reduced induced curvature.

Sample preparation: A sodium calcium silicate glass test piece (50 mm × 50 mm diameter and 0.4 mm width) was cut from a mother sheet formed by a tin floating glass process. The test piece was heat-treated in a muffle furnace at 550 ° C for 0.5 hour in air (oxidizing atmosphere) and heat-treated at 550 ° C for 2.0 hours. The test piece was cooled to room temperature and then chemically strengthened by immersion in a beaker of molten KNO ₃ controlled to a temperature of 440 ° C for 24 hours. The test piece was cooled and rinsed with water to remove the solidified salt. Check a minimum of three test strips for each parameter. The treated specimen deflection was measured from the measured surface profile using a non-contact optical plotter. Flexure is the peak-to-valley height measured along the line drawn between the midpoints of the opposite edges of the square test piece.

Results: The average deflection is given in Table II with respect to the pretreatment parameters, where positive deflection indicates the convex curvature of the rich surface and negative deflection indicates the concave curvature of the rich surface. For commercial purposes, such as for use in personal electronic devices and flat panel displays, acceptable deflection is currently about 0.1% linear span and 50 micron for 50 mm span.

The heat treatment parameters in air at 550 ° C for 2.0 hours prior to chemical strengthening produced a deflection of the target of less than 50 microns in this case. The surface compression and hardening depth resulting from chemical strengthening is measured using an ellipsometer. Since the longer chemical strengthening time was used in Example 2, the hardening depth was significantly larger and the surface compression amount was significantly lower than in Example 1.

Table 2: Heat treatment (given in temperature (degrees Celsius) and time (hours)) and average deflection (micron) after chemical strengthening.

[Table 2]

For the 550 ° C, 2.0 hour air heat treatment conditions after chemical strengthening, the average deflection is 37.3 microns (rich side convex surface), the average surface compression is 582 MPa for the rich surface and 596 MPa for the lean surface, the average hardening depth is 24.8 μm for the rich surface and For a lean surface it is 22.2 microns. The test piece, which did not undergo heat treatment but undergoes equivalent chemical strengthening, had an average deflection of 110.3 microns (rich side convexity).

Example 3

Example 3 demonstrates the empirical relationship between heat treatment time and reduced induced curvature.

Sample preparation: A sodium calcium silicate glass test piece (50 mm × 50 mm diameter and 0.4 mm width) was cut from a mother sheet formed by a tin floating glass process. The test piece was heat treated in a muffle furnace in air (oxidizing atmosphere) at 525 ° C for different durations, as shown by the square root of time (hours) in the x-axis of the graph 200. The test piece was cooled to room temperature and then chemically strengthened by immersion in a beaker of molten KNO ₃ controlled to a temperature of 440 ° C for 24 hours. The test piece was cooled and rinsed with water to remove the solidified salt. Check a minimum of three test strips for each parameter. The treated specimen deflection was measured from the measured surface profile using a non-contact optical plotter. Flexure is the peak-to-valley height measured along the line drawn between the midpoints of the opposite edges of the square test piece.

Results: The square root of the average deflection versus heat treatment time is given in Figure 200, where positive deflection indicates the convex curvature of the rich surface. For commercial purposes, such as for use in personal electronic devices and flat panel displays, acceptable deflection is currently about 0.1% linear span and 50 micron for 50 mm span.

Scheme 200 demonstrates the square root and chemical strengthening of the average deflection (micrometer) relative to the heat treatment time (hours) after heat treatment at 525 °C. For the example glass test piece, assuming that 600 ° C is the highest heat treatment temperature ("m") and 0.00111 hours / ( ° C) ² is the empirical constant ("n"), it can be used for deflection to reduce to an acceptable value. The empirical relationship between the heat treatment time "t" (hours) (about 0.1% of the length of the test piece) is roughly given by t = 0.0011 × (600 - T) ² hours, where T is the heat treatment temperature (°C). One of ordinary skill in the art can use the empirical relationships shown herein to develop similar heat treatment temperatures and heat treatment time relationships for other glass compositions and glass substrates.

Exemplary method

Floating glass: During the manufacture of floating glass, the glass can be cooled in a carefully controlled manner to reduce the internal stress, which is called "annealing". The process temperature and time can be varied before, during or after annealing so that the heat treatment process can be incorporated on-line. This typically involves using a longer period of time at elevated temperatures than annealing, where the extended duration may depend on the selected temperature. The heat treatment can be carried out in an oxidizing atmosphere, a neutral atmosphere or a reducing atmosphere or a stepwise combination thereof. The curvature reducing heat treated substrate can then be chemically strengthened in an ion exchange process and produce less curvature. Chemical strengthening can be performed immediately after the curvature control processing method or at a later time.

The temperature used for the heat treatment may also be subject to the physical and chemical properties of the unreinforced glass to be chemically strengthened. The temperature change for the heat treatment process can be made by widening with a suitable support system to avoid dimensional distortion in a thin glass sheet undergoing heat treatment. The process for making glass, such as by floatation, can be varied such that one or more of the curvature control methods can be applied at higher temperatures.

Preheating device: The preheating device is typically used prior to chemical strengthening to heat the glass article just prior to immersion in the molten exchange medium. Such preheating helps to prevent glass breakage, such as occurs when the cold glass article is immersed in the hot melt exchange medium.

According to the new invention, in the case of glass thus produced, such as floating glass intended for use in a chemical strengthening process, the temperature and time for preheating the device can be varied by increasing the time and/or temperature as described herein. To achieve the heat treatment temperature and/or heat treatment time conditions, the curvature reduction heat treatment can be achieved in the preheating device.

At higher temperatures, a suitable support system can also be used to avoid dimensional distortion in the thin glass sheets. The heat treatment can be carried out in an oxidizing atmosphere, a neutral atmosphere, a reducing atmosphere or a stepwise combination thereof. The glass can then be directly immersed in the exchange medium to perform chemical strengthening in an ion exchange process and produce less curvature.

Batch process: A batch of float glass thus produced can be placed in a suitable furnace and maintained at a sufficient high temperature for a sufficient period of time in an oxidizing atmosphere, a neutral atmosphere, a reducing atmosphere or a stepwise combination thereof to achieve a heat treatment process. At higher temperatures, a suitable support system can be used to avoid dimensional distortion in the thin glass sheets. After cooling, or at a later time, the glass can then be chemically strengthened in an ion exchange process via, for example, immersion in a molten salt or application of a salt-containing paste, and produces less curvature.

Applicants have performed chemical strengthening in the atmosphere of 40% O ₂ + 60% N ₂ , 60% O ₂ + 40% N ₂ , 100% O ₂ , pure nitrogen, and 95% N ₂ + 5% H ₂ using the aforementioned heat treatment. In each case, a reduction in deflection was observed within the reference specimen. The curvature produced by chemical strengthening is reduced by heat treatment to a high temperature under conditions such as an oxidizing atmosphere, a neutral atmosphere, a reducing atmosphere, or a stepwise combination thereof before chemical strengthening.

The curvature of the chemically strengthened glass article can be controlled, including thin glass articles. The surface of the formed glass article is visible in optical and finishing (metering) quality similar to that produced by the floating manufacturing process. However, the glass surface does not require grinding, polishing, etching or milling. Also, there is no need to apply a permanent surface coating to the formed glass article. The total alkali concentration on the glass surface does not change. Therefore, the chemical stability is still similar to the chemically stable quality produced by such a manufacturing process using a floating manufacturing process.

The heat treatment process can be extremely simple and can be carried out in the form of an in-line process that is performed by careful control of temperature and time before, during or after annealing of the floating glass. The heat treatment method can be performed at any time before chemical strengthening. An example is in a preheater placed above a molten exchange medium. In this configuration, the curvature control heat treatment method can be implemented in the chamber in a preheating process to avoid breakage, or by a separate preheating process. Avoid rupture before immersion in ion exchange. Alternatively, many glass articles may be subjected to a curvature reduction heat treatment process for a sufficient period of time in an oxidizing atmosphere, a neutral atmosphere, a reducing atmosphere, or a stepwise combination thereof in a suitable furnace maintained at a sufficient temperature.

3 is a flow chart illustrating an exemplary process 300 for fabricating a reinforced substrate having reduced induced curvature using heat treatment.

At step 302, a glass substrate having different regions (such as "rich processing" regions and "lean processing" regions) in a glass structure including a bulk alkali ion is provided. The substrate glass provided may be sodium aluminosilicate glass or aluminosilicate glass. The regions may be disposed, for example, opposite one another in the substrate, and may be diametrically opposed in accordance with an embodiment. The glass substrate can have variations in different regions, such as changes in chemical composition and/or chemical structure. An example of a change in chemical composition is the amount of tin located in different regions of the glass. An example of a chemical structural change is that tin is present in different regions of the glass with different valences Sn ²⁺ and Sn ⁴⁺ . Changes in chemical composition and/or chemical structure in the lean treatment zone can distinguish it from the rich treatment zone.

At step 304, the provided substrate glass is heated to a temperature T1 for a duration P1 during the heat treatment process. T1 can vary from 250 ° C to the highest heat treatment temperature associated with the substrate glass twistable temperature (such as above 600 ° C for soda lime silicate glass or 800 ° C for sodium aluminosilicate glass). The period P1 can vary between 0.05-20 hours or longer.

At step 306, the heat treated substrate glass is removed from heating and allowed to cool, such as to ambient temperature or another temperature (such as About 150 ° C), resulting in a cooled heat treated substrate. The cooling process is not controlled as in annealing. In contrast, annealing requires a specified time of cooling at a predetermined temperature range and a specified cooling rate. According to other exemplary embodiments, step 306 may be omitted or repeated.

At step 308, the cooled heat-treated substrate glass is again heated to a temperature T2 for a period of time P2 in a subsequent heat treatment process. T2 can be at 250 ° C to the required exchange temperature The change between degrees makes the immersion into the molten salt bath will not cause thermal shock rupture of the substrate. The period of time P2 may vary between 0.05-20 hours or more or 0.01-50 hours or more. As an option, step 308 can also be performed as part of a reduced curvature heat treatment. According to other exemplary embodiments, step 308 may be omitted.

At step 310, the substrate is immersed in the heat-treated in a molten KNO ₃ at the temperature T3 of the exchange medium. The exchange medium provides intrusive alkali ions, also known as potassium. T3 can vary widely from 200 °C to 1,000 °C and can be, for example, 450 °C.

At step 312, the submerged substrate undergoes an ion exchange duration P3. The time period P3 can vary widely from 0.1 to 50 hours. During ion exchange, a compressive stress layer is formed in the reinforced substrate. The compressive stress layer has a depth of from about 1 to 500 μm, and in one embodiment from about 5 to 200 μm. The amount of induced curvature from chemical strengthening is reduced in the strengthened substrate via the heat treatment in step 304. According to an embodiment, the net bending moment at about the median plane in the reinforced substrate can be about zero.

The description of the present invention is intended to be useful in a wide range of applications, and the above discussion is not intended to be, and should not be construed as limiting. The terms, descriptions, and figures used herein are to be construed as illustrative only and not limiting. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the principles of the invention. While the examples have been described with reference to the drawings, various modifications of the examples can be made by those skilled in the art without departing from the scope of the appended claims.

This application is based on US Provisional Application No. 61/714,054, entitled "Strengthened Glass and Methods for Making" by Arun K. Varshneya, filed on October 15, 2012, and non-temporary US application on October 15, 2013. Application No. 14/054,489, the disclosure of which is incorporated herein in its entirety by reference.

Industrial applicability

According to the present invention, it is possible to obtain a reduced induced curvature and improved physical properties Chemically strengthened glass, such as higher strength, higher wear resistance, and/or higher thermal shock resistance, and a method of making the chemically strengthened glass.

Claims (18)

A method of manufacturing a reinforced substrate, the method comprising: providing an inclusion A floating glass substrate having a width of about 25.0 mm, characterized by having a chemical composition and a glass chemical structure including a bulk alkali ion having an average ionic radius, and including a rich processing region disposed in the substrate provided opposite to each other And a dimension region of the lean region; determining a heat treatment temperature for producing a reduced induced curvature in the substrate after chemical strengthening, based at least in part on a maximum heat treatment temperature associated with the substrate and the chemical composition; a heat treatment time for reducing the induced curvature in the substrate after chemical strengthening, based at least in part on the heat treatment temperature and the highest heat treatment temperature; heating the provided substrate to a heat treatment to About 250 ° C and The heat treatment temperature after the heat treatment temperature of the highest heat treatment temperature is about 0.001-50 hours, wherein the heat treatment temperature About 325 ° C, the heat treatment time Approximately 2 hours to produce a heat treated substrate; providing an exchange medium comprising an invading alkali ion having an average ionic radius greater than the average ionic radius of the host alkali ion; exposing the heat treated substrate to the exchange medium And performing ion exchange to chemically strengthen the substrate while exposing the heat-treated substrate to the exchange medium to produce a strengthened substrate, wherein the strengthened substrate comprises a compressive stress layer having a depth of about 1-500 μm, wherein the the heat treatment temperature and heat treatment time line induction of curvature of the substrate was reduced to produce the reinforced at least in part on determined to satisfy the following relation: t n . ( m - T ) ² "t" is the heat treatment time (hour), "n" is the empirical constant, "m" is the highest heat treatment temperature (°C), and "T" is the heat treatment temperature (°C). Wherein the strengthened substrate has a reduced induced curvature after chemical strengthening based on the heat treatment. The method of claim 1, wherein the width of the substrate provided About 2.0 mm, wherein the net bending moment about the median plane in the reinforced substrate is about zero. The method of claim 1, wherein the heat treatment temperature is about 450 to 650 °C. The method of claim 1, wherein the heat treatment temperature is about 400 to 750 °C. The method of claim 1, wherein the heat treatment temperature About 400 ° C, the heat treatment time About 2 hours. The method of claim 1, wherein the reinforcing substrate has a compressive stress layer having a depth of about 5 to 200 μm. The method of claim 1, wherein the performing the ion exchange is carried out during an ion exchange time of about 0.1 to 50 hours. The method of claim 1, wherein the ion exchange is carried out at an ion exchange temperature of from about 200 ° C to 1,400 ° C. The method of claim 1, wherein the substrate is flat. The method of claim 1, wherein the heat treatment time 0.5 hours, and if the heat treatment time is about 0.5-1 hour, the heat treatment temperature About 500 ° C; if the heat treatment time About 1-3 hours, the heat treatment temperature About 475 ° C; if the heat treatment time About 3-6 hours, the heat treatment temperature About 450 ° C; if the heat treatment time About 6-12 hours, the heat treatment temperature About 425 ° C; if the heat treatment time The heat treatment temperature is about 12-18 hours About 400 ° C; and if the heat treatment time About 18-25 hours, the heat treatment temperature About 375 ° C. The method of claim 1, wherein the heat treatment time 0.5 hours, and if the heat treatment time is about 0.5-1 hour, the heat treatment temperature About 575 ° C; if the heat treatment time About 1-3 hours, the heat treatment temperature About 550 ° C; if the heat treatment time About 3-6 hours, the heat treatment temperature About 525 ° C; if the heat treatment time About 6-12 hours, the heat treatment temperature About 500 ° C; if the heat treatment time The heat treatment temperature is about 12-18 hours About 475 ° C; and if the heat treatment time About 18-25 hours, the heat treatment temperature About 450 ° C. The method of claim 1, wherein the heat treatment time 0.5 hours, and if the heat treatment time is about 0.5-1 hour, the heat treatment temperature About 650 ° C; if the heat treatment time About 1-3 hours, the heat treatment temperature About 625 ° C; if the heat treatment time About 3-6 hours, the heat treatment temperature About 600 ° C; if the heat treatment time About 6-12 hours, the heat treatment temperature About 575 ° C; if the heat treatment time The heat treatment temperature is about 12-18 hours About 550 ° C; and if the heat treatment time About 18-25 hours, the heat treatment temperature About 525 ° C. The method of claim 1, further comprising cooling the heat treated substrate to a cooling temperature of about 150 ° C to produce a cooled heat treated substrate; and heating the cooled heat treated substrate to About 250 ° C and The heat treatment temperature of the highest heat treatment temperature is followed by a heat treatment time of about 0.01 to 50 hours to produce the heat-treated substrate. The method of claim 1, wherein at least one of a chemical composition and a chemical structure of the substrate in the substrate comprises a change, and at least one of the chemical composition and the chemical structure in the lean region is treated with the rich The area is different. The method of claim 1, wherein the exchange medium is a liquid, a solid, a gas, and a mixture thereof One of the compounds. The method of claim 1, wherein the rich processing region and the lean processing region are disposed diametrically opposite one another in the substrate. The method of claim 1, wherein the method is one of a continuous process and a batch process. The method of claim 1, wherein the substrate comprises one of alkali aluminosilicate glass and sodium aluminosilicate glass.